Introduction

The number of prenatal care visits plays an important role in measuring the adequacy of prenatal care during pregnancy. A prenatal care visit is defined as a series of regular contacts between a health care provider, typically a physician, and a pregnant woman that take place at scheduled intervals between the confirmation of pregnancy and the initiation of labour. The primary function of this care is to monitor the progress of pregnancy to identify complications, to provide information to the women on beneficial practices, and to co-ordinate the involvement of other providers in the mother's labour and the delivery of the newborn (Mustard, CA; 1993).

This concept provides information on the methods used in MCHP research to identify and count the number of prenatal care visits, and how this count assists in developing indicators that are used to describe and measure the adequacy of prenatal care in Manitoba.

NOTE: The term prenatal care visits (PCV) is synonymous with prenatal care (PNC) and prenatal doctor visits.

Methods to Identify Prenatal Care Visits from the MCHP Data Repository

Over time, different methods have been used to identify prenatal care visits in the Data Repository. This is due to changing tariff codes, the inclusion or exclusion of specific pregnancy-related laboratory and diagnostic tests, and the availability of different data.

Prior to October 2000, PNC visits were billed once per pregnancy using a global tariff recorded in the Medical Services data. Using the Medical Services data alone, the actual number of prenatal care visits could not be accurately counted. Therefore, three datasets are used to achieve a more accurate count of the number of prenatal visits:


• Medical Services / Medical Claims;
  
• Hospital Abstracts; and
  
• Midwifery Summary Reports

1. Medical Services / Medical Claims Data

Over time, the tariff codes used to define prenatal care visits have changed.

The earliest method used to identify prenatal care visits (Fraser et al., 1993) included the following tariff codes, AND required a diagnosis code related to pregnancy as these tariff codes are not specific to prenatal care:

• 8501 - Office Visits, Regional History and Examination;
  
• 8507 - Office Visits, Subsequent Visit;
  
• 8540 - Office Visits, Complete History and Physical Examination, New Patient.

Specific prenatal visit tariff codes with prefix = 3 (obstetrical/maternity) were added as early as 1970, but more reliably coded beginning in 1984. These are "global" prenatal/post-natal tariff codes (e.g. one billing per pregnancy):

• 4801 - Caesarean section, including pre and post-natal visits with or without sterilization;
  
• 4821 - Pregnancy and maternity, confinement, including ante-partum and post-partum visits;
  
• 4823 - Preg & mat complete ante-partum and post-partum visits, excluding confinement.

Beginning in February 2000, relevant tariff codes for prenatal / post-natal visits were introduced, with prefix = 7 (visits). These tariffs are not global and allow multiple billings per pregnancy, one for each prenatal care visit:

• 8400 - Complete pre-natal assessment;
  
• 8401 - Pre-natal visit - subsequent;
  
• 8402 - Post-natal visit; and
  
• 8416 - Midwifery assessment/report.

This 2000 change allows for a more accurate count of the actual number of prenatal care visits per patient directly from the Medical Services data.

2. Hospital Abstracts Data

Historically, the hospital abstracts data has recorded the number of prenatal care visits for each pregnancy-related abstract that is completed.

This record of the number of prenatal visits is provided to the hospital by all the care providers involved in the patients prenatal care during the pregnancy, and recorded at the time of abstracting.

The variable that provides the number of prenatal care visits has changed over time in the different versions (e.g. HAUM, DAD) of the hospital abstract data.

3. Midwifery Summary Reports

The Midwifery Summary Reports data is less commonly used in the count of prenatal visits, but is an additional source for the very small number of women getting care only from a Midwife and having a home birth. However, this number should be included in the Hospital Abstracts total count of prenatal visits.

Specific MCHP Prenatal Care Research Methods

This section describes the specific methods used in different MCHP research over time.

1. Fraser et al. (1993)

Ambulatory claims for pregnancy care consist of three broad categories of service: office visits, in-office or laboratory diagnostic tests, and referrals for consultation.

Office visits were defined as any claim with a tariff code of 8501, 8507 or 8540 AND an ICD-9-CM diagnostic code indicating a complication related to pregnancy (ICD-9-CM 640-648), other indications for care in pregnancy, labour and delivery (ICD-9-CM 650-659), or complications occurring in the course of labour and delivery (ICD-9-CM 660-669). Additionally, claims with ICD-9-CM diagnostic codes for normal pregnancy (V22), or supervision of high-risk pregnancy (V23) were also defined as office visits.

For specific diagnostic tests, physician and laboratory claims were defined as associated with prenatal care regardless of whether the claim contained a pregnancy-related diagnosis code. The selected tests were glucose monitoring (tariff code 9140, 9141, 9142 or 9144), haemoglobin (tariff code 9150), urinalysis (tariff codes 9641 or 9644), pap smear (tariff code 9795) or a hormonal pregnancy test (tariff code 9521). The first three tests are the standard monitoring tests in pregnancy.

2. Brownell et al. (2010)

In the Evaluation of the Healthy Baby Program deliverable by Brownell et al. (2010), they focused on prenatal care visits data found in the Medical Services data. Usually, tariff codes 8400 (Complete Prenatal Assessment) and 8401 (Prenatal Visit Subsequent) are used to identify a Prenatal Care Visit.

However, in this research they were interested in measuring the adequacy of prenatal care by assigning a R-GINDEX value to a patient, so the usual approach of counting prenatal care visits had to be enhanced, otherwise the adequacy of prenatal care would be understated. This approach involved looking at tariff codes, lab work and diagnostic tests, and ICD-9-CM diagnosis codes in the Medical Services data.

Prenatal Care Visits Data in the Medical Services Data

The research used the following tariffs, lab related work/diagnostic tests, and ICD-9-CM diagnoses codes to define and identify prenatal care visits from the Medical Services data.

Prenatal Care Visit Tariffs

8400 - Complete Prenatal Assessment
8401 - Prenatal Visit Subsequent

Office Visit Tariffs

8501 - Office visits, Regional History and Examination
8507 - Office visits, subsequent visits
8540 - Office visits, complete history and physical examination, new patient
8509 - Office visits

Lab Related Work / Diagnostic Tests (** - see ** NOTE in Method II section below)

9140, 9141, 9142, 9144 - Glucose Monitoring
9150 - Hemoglobin
9641, 9644 - Urinalysis
9795 - Pap Smear
9521 - Hormonal Pregnancy Test

ICD-9-CM Codes

640-648 - Diagnostic code indicating a complication related to pregnancy
650-659 - Other indications for care in pregnancy, labor and delivery
660-669 - Complications occurring in the course of labor and delivery
V22 - Normal Pregnancy
V23 - Supervision of High Risk Pregnancy

Identifying PCVs By Visit Type Flags

In the Medical Services data, keep only those records that have prefix type = 7 or 8.

NOTE: a prefix of 7 = in office visits and a prefix of 8 = laboratory work

Create 6 flags to identify the types of visits:


1. if tariff in ('8400') then FPV_tariff = '1'
   
2. if tariff in ('8401') then SPV_tariff = '1'
   
3. if tariff in ('8501', '8507', '8540', '8509') then office_visit_tariff = '1'
   
4. if tariff in ('9140', '9141', '9142', '9144', '9150', '9641', '9644', '9795', '9521') then test_tariffs = '1' ( ** - see ** NOTE in Method II section below)
   
5. if '640' <= diag <= '648' or '650' <= diag <= '659' or '660' <= diag <= '669' then ICD9_diag = '1';
   
6. if diag in ('V22', 'V23') and prefix = '7' then preg_visit_prefix7 = '1'

Methods to Identify Prenatal Care Visits

The research developed two separate methods for identifying all the PCVs recorded in the Medical Services data so that when combined, they had a more accurate count of the number of PCVs.

METHOD I - Tariff and Diagnosis Codes

Method I looked at specific tariff and diagnoses codes, but did not include any lab claims or diagnostic tests. The reason for this is because including them would inflate the actual number of PCVs. The steps involved in Method I are:


1. Keep only physician records where:

   FPV_tariff = '1' or SPV_tariff = '1' or (office_visit_tariff = '1' and ICD9_diag = '1') or preg_visit_prefix7 = '1'

2. Evaluate all physician records belonging to the mother and keep only those records that fall within the gestation period of her baby.
   
3. Remove those physician visits that occurred alongside a hospital admission on the date of delivery.
   
4. Identify the date of the first PCV to a physician. Sort all the physician visits by date. The record appearing first will be assigned the date of first PCV. All visits after this first PCV date will be considered subsequent visits.
   
5. Create a counter that counts the total number of PCVs (PCVs = initial visit + all subsequent visits).


METHOD II - Lab Claims and Diagnostic Tests

Method II accounts for those remaining moms that were found to have no PCVs using Method I. In this case, relevant lab claims and diagnostic tests are used to count the number of prenatal visits and assign the date of the first PCV. The steps involved in Method II are:


1. Pull all diagnostic tests and laboratory claims within the gestation period for those remaining moms found to have no PCVs using Method I (i.e.: where put(obphin, $nocare.) = 'Y' and test_tariffs = '1');
   
   ** NOTE: These tariffs would include: Glucose Monitoring, Hemoglobin, Urinalysis, Pap Smears and Hormonal Pregnancy tests, as defined above.
   
   
2. Repeat steps 2-5 from Method I above using all of the records found for lab claims and diagnostic tests.

NOTE: Method II will result in very few additional records being found.

SAS Code

The SAS code used to identify prenatal care visits in this research is available in the SAS code and formats section below (internal access only).

3. Heaman et al. (2012)

In the Perinatal Services and Outcomes in Manitoba deliverable by Heaman et al. (2012), the method to define PCVs differed from the method used in the 2010 deliverable. Heaman et al. investigated prenatal care visits data using three different data sources in the MCHP Data Repository.

The three data sources investigated for prenatal care visit data included:

1. Prenatal Care Visits in the Medical Services Data

The following tariff codes and diagnosis codes were used to identify prenatal care visits in the Medical Services data:


• 8400 - Complete Prenatal Assessment
  
• 8401 - Prenatal Visit Subsequent
  
  
• If one of the following tariff codes was recorded, along with a diagnosis of pregnancy (if "640"<=diag<="648" or "650"<=diag<="659" or "660<=diag<="669" or diag in ("V22","V23")) in the same record, then the visit was counted as a prenatal care visit (PCV):
  
  
  • 8501 - Office visits, Regional History and Examination
    
  • 8507 - Office visits, subsequent visits
    
  • 8509 - Office visits
    
  • 8529 - Regional Intermediate Visit - Regional or Subsequent Visit or Well Baby Care
    
  • 8540 - Office visits, complete history and physical examination, new patient
    
  • 8550 - Consultation

NOTES:

• All of these tariff codes must start with a prefix = 7 (in office visits).
  
• All services must fall within the relevant gestation period.
  
• Tariffs for laboratory claims and diagnostic tests were not used to identify PCVs in this research project.

2. Prenatal Care Visits in the Hospital Discharge Abstract Data

Women do not receive their prenatal care in hospital. Typically, they receive it from physicians in clinics, but this is not always well recorded as a prenatal visit. When a women is admitted to hospital to give birth, the hospital is supposed to receive information from all the providers (physicians, midwives and nurses providing care in the north) involved in the prenatal care experience. The information received is used to calculate the number of prenatal care visits and the date of the first prenatal care visit, and these two data elements are recorded in the corresponding Hospital Abstracts Data.

3. Prenatal Care Visits in the Midwifery Summary Reports Data

Upon investigation, it was found that the information available from the Midwifery Discharge Summary Reports data could not be used to accurately count the number of prenatal care visits.

Identifying the Total Number of Prenatal Care Visits

In this project, the total number of prenatal care visits for each patient was determined by using the higher count of prenatal care visits calculated from either the Medical Services data or from the Hospital Abstracts data.

SAS Code

This method of identifying prenatal care visits was also used in The 2019 RHA Indicators Atlas by Fransoo et al. (2019) . The SAS code used in the 2019 deliverable is available in the SAS code and formats section below (internal access only).

Prenatal Care Health Indicators

In Heaman et al. (2012), three indicators were developed and used to measure and investigate the adequacy of prenatal care, including:


• Late initiation of prenatal care - begins after the first trimester of pregnancy (more than 13 weeks gestation). Please read the section titled Late Initiation of Prenatal Care in Heaman et al. (2012) for more information.
  
• Low number of prenatal care visits - less than five prenatal care visits prior to delivery. Please read the section titled Low Number of Prenatal Visits in Heaman et al. (2012) for more information.
  
• Revised-Graduated Prenatal Care Utilization Index (R-GINDEX) - measure of the adequacy of prenatal care. Please read the section titled Inadequate Prenatal Care in Heaman et al. (2012) for more information.

Cautions / Limitations

Please be aware of the following cautions / limitations when working with prenatal care visits:


• In research prior to February 2000, prenatal care visits were typically excluded from our Ambulatory Visits definition because of tariff coding issues (e.g. the use of global billing with only one billing/claim recorded per pregnancy, and thus not being able to count the actual number of prenatal care visits). However, specific prenatal and post-natal care visit tariff codes were introduced in February 2000, and the current ambulatory visits definition now includes prenatal and post-natal visits.
  
  
• The use of Medical Services data only may undercount the actual number of prenatal visits in the population. The use of Hospital Abstract prenatal care related data allows for a more complete look at prenatal care information in some situations, especially data from Northern regions.
  
  
• In some cases, the number and timing of the first PCV was estimated from Hospital Abstracts and Medical Services data, and the accuracy of our estimates may be affected by several factors, such as missing PCV records in the hospital chart or receipt of PCV from healthcare providers who do not submit claims for prenatal care services.
  
  
• As well, inaccurate ascertainment of gestational age may affect assignment to a PVC utilization category.
  
  
• The indicators only reflect the quantity of PCV; they indicate nothing about the content, clinical adequacy, or quality that is provided.
  
  
• The R-GINDEX is based on the ACOG (American College of Obstetricians and Gynecologists) recommendations for number of visits for low risk pregnant women; the effectiveness of this standard has not been assessed through rigorous scientific testing, nor has adequacy of care for women with high risk pregnancies been operationalized (Alexander & Kotelchuck, 2001). For the purpose of calculating the indicators of prenatal care in Heaman et al. (2012), a prenatal visit was defined as a visit to a health professional (i.e., physician, midwife or nurse practitioner) where some kind of medical or healthcare was performed to take care of the pregnancy. Other forms of prenatal health services were not included in this definition, such as attendance at prenatal classes or Healthy Baby Community Support Programs.
  
  
• Analysis of the indicators was limited to hospital births because we found that prenatal care was not well recorded in the Midwifery Summary Reports.
  
  
• The overall higher rates of a low number of prenatal visits for women in the North found in Heaman et al. (2012) requires further exploration; the sudden increase in rates in the North from 2006/07-2008/09 suggests some health system or provider issue (i.e., problems with access to care) or a data quality issue as opposed to patient choice.